Reciprocating slat-type conveyors (also referred to as “conveyor systems,” “reciprocating slat conveyors,” or “conveyors”) generally include a plurality of elongated slats (also referred to as “conveyor slats,” “floor slats,” or “deck slats”). Some conveyors are referred to by their trademark names of LIVE FLOORS® and “WALKING FLOOR®.” The conveyors are generally used in the load-holding compartment of load transport vehicles (e.g. a mobile cargo trailer, bed of a truck (truck bed), rear portion of a semi-trailer, or container portion of a van-truck). The load-holding compartment has a front end toward the front of the compartment (e.g. in a truck the front end would be the end toward the driver compartment) and a back or rear end (e.g. in a truck the back end would be the end into which the load would be inserted and from which the load would be removed). The slats are arranged side-by-side to form the floor of the load-holding compartment so that they extend longitudinally to the framework of the load-holding compartment. A “load” may be, for example, silage, grain, fertilizer, soil, sand, shredded documents, chipped wood, sawdust, garbage, or any particulate matter.
The slats are generally grouped in groups of two or more slats (groups of n slats). Groups may also include one or more stationary slats. For the purpose of description, respective slats from each group will be referred to as a “set.” The slats in each set move simultaneously in one direction (the “load-conveying direction” or “conveying direction”) and then return (in the “load-retracting direction” or “retracting direction”) to the beginning position. The slats' back and forth movement results in a step-wise advance of the load positioned on the floor followed by a retraction of the slats without moving the load. If a truck were being loaded, the load-conveying direction would be toward the front end of the load-holding compartment and the load-retracting direction would be toward the rear end of the load-holding compartment. If a truck were being unloaded (a more typical use), the load-conveying direction would be toward the rear end of the load-holding compartment and the load-retracting direction would be toward the front end of the load-holding compartment.
Reciprocating slat conveyors can be categorized based on the number of “steps” each group of slats performs in the load-retracting direction (e.g. if the slats in a three-slat group each retract individually, it is a three-step system, but if only two slats of a three-slat group retract, and the third is held in place, it is a two-step system. Another categorization is based on whether the loading/unloading motion is continuous (conveying motion by a majority of slats doesn't stop moving the load while a minority retract) or non-continuous (conveying motion stops while each slat set retracts).
U.S. Pat. No. 4,856,645 to Hallstrom (which is herein incorporated-by-reference in its entirety) describes a two-step non-continuous reciprocating slat type conveyor that includes two longitudinally extending, laterally spaced apart, first and second sets of alternating slats arranged for longitudinal sliding movement on the plane of the bed. Interposed between adjacent reciprocating slats is a third fixed slat mounted immovably to the framework. A pair of double-acting hydraulic cylinders are provided to move the sets of reciprocative slats longitudinally, the first set of reciprocative slats being connected to the first cylinder and the second set being connected to the second cylinder, so that adjacent reciprocative slats are able to move independently of each other while every other reciprocative slat operates in unison off the same drive, whereby both sets of reciprocative slats can be moved in the conveying direction simultaneously, and each set of reciprocative slats can be moved in the opposite, retracting direction independently of the other.
U.S. Pat. No. 4,962,848 to Foster (which is herein incorporated-by-reference in its entirety) describes a two-step non-continuous reciprocating floor conveyor that includes groups having two movable floor members and a third fixed, immovable floor member. The primary difference between the invention described in the Foster patent and the invention described in U.S. Pat. No. 4,856,645 to Hallstrom is in the location of the moving floor members in relation to the fixed, immovable floor member.
U.S. Pat. No. 3,534,875 to Hallstrom (which is herein incorporated-by-reference in its entirety) describes a three-step continuous reciprocating slat-type conveyor. In the Hallstrom '875 patent, groups of at least three elongated slats are arranged side by side to form a conveyor-type truck bed. The slats of each group are connected to a drive mechanism in such a manner that there are always a greater number of slats of each group moving simultaneously in the conveying direction while the remaining slat or slats of the group move in the opposite, retracting direction. Drive means are included that are operable to move more than half of the number of slat members of each group simultaneously in a conveying direction and to move the remainder of the slats of each group in the opposite direction at a higher rate of speed. For example, the Hallstrom '875 patent describes an embodiment in which there are two sets of slats conveying and one set of slats retracting.
U.S. Pat. No. 4,143,760 to Hallstrom (which is herein incorporated-by-reference in its entirety) describes a three-step non-continuous reciprocating slat-type conveyor in which the slats are connected to a fluid pressure drive mechanism that is operable to move all of the slats of each group from a start position simultaneously in a load-conveying direction and then to move the slats of each group sequentially (in sets of respective slats) in the opposite, retracting direction from the advanced position back to the start position. The slats of each group are interengaged releasably in the conveying direction to ensure simultaneous movement.
U.S. Pat. No. 4,793,468 to Hamilton (which is herein incorporated-by-reference in its entirety) describes an apparatus, and a related method, for controlling a four-step continuously moving floor having multiple sliding slats, to produce a practically uniform load-moving force on a load carried on the apparatus. The slats are reciprocated back and forth by hydraulic cylinders, each of which controls a set of slats that are moved together. At any given time, a majority of slats is moving together in the desired direction, and carrying a load in this direction at a nearly uniform velocity. The remainder of the slats is moved in a reverse direction, but at a speed that is a multiple of the forward speed of the majority of the slats. Each set of slats is moved through a forward stroke at a relatively low speed; then through a backward stroke at a higher speed.
U.S. Pat. No. 4,580,678 to Foster (which is herein incorporated-by-reference in its entirety) describes a six-step continuously moving conveyor that uses two separate sources of hydraulic pressure, one for advancing the floor slat members and another for retracting the floor slat members. A majority of the floor is always moving in the conveying direction while a minority of the floor is being retracted at a greater rate of speed.